The invention relates generally to the provision of power to micro devices such as micro machines and micro actuators. In particular, it deals with activation of micro devices by optical radiation transmitted through optical fibers.
Micro machines and micro actuators are becoming well known in the technical world. Typically they are miniature mechanisms with dimensions ranging from 100 micrometers to several millimeters.
Their manufacture became possible with the advent of new technologies such as the various micro lithographic techniques developed for the semiconductor industry. As improvements are made in these technologies, ever smaller and more complex machines and structures are becoming possible on a microscopic scale.
At present, micro devices are typically powered by electricity. While electrical motor drives are generally convenient, transmission of electrical energy becomes increasingly difficult as cable cross sectional area decreases and distances increase between power source and device.
It is well established from physics that a wire's resistance increases as its length increases and as its cross sectional area decreases. To maintain a fixed power or electrical current as distances increase and cross sectional areas decrease, thus requires that the voltage be significantly increased. With ever finer wires required for smaller and smaller devices and with a desire to further remote the power source from the active element, higher and higher voltages are required as for example in small piezoelectric drives. Problems arise as voltages increase because shielding the electrical circuit from surroundings, which are typically grounded, becomes more important but also more difficult to achieve in small packaging.
The principles of electromagnetic theory thus make it very difficult to use present state of the art micro devices in remote areas where only small access channels are available. A particularly difficult application would be using micro devices inside a human body, where, additionally from first principles, electrical signals and power may be undesirable.
An alternative power transmission principle, which can reduce electrical safety concerns, would be a mechanical, rotating shaft. In fact, such mechanical devices are used for instance to remove plaque from calcified arteries. This approach, however, also has problems as device dimensions and available transmission channels become restricted. Stiffness and torque resistance of the transmission shaft limit power available to the remote device.